1. Field of the Invention
Creep corrosion is the corrosion of copper and silver metallization on printed circuit boards (PCBs) and the subsequent creep (migration) of the sulfide corrosion products across the PCB surface, thereby, electrically shorting neighboring circuit board features and causing the electronic device to malfunction.
2. Description of the Related Art
High levels of sulfur-bearing gaseous contamination along with the synergistic effects of humidity and other contaminants such as ozone and nitrogen dioxide can cause creep corrosion on printed circuit boards.
The contamination in the air can be measured by chemical analysis or by reactive monitoring. Chemical analysis of the air can determine the composition of the air including many of its contaminants such as sulfur-bearing gases. Reactive monitoring measures the corrosion rates of copper and silver coupons (metal foils) exposed to air. Reactive monitoring does not measure the composition of the air. It does give some information about the contaminants in the air. For example, if the corrosion product consists of a thick layer of sulfide, it can be readily concluded that the air is high in sulfur-bearing contaminants. But neither of these methods gives any direct indication of whether the contamination levels are severe enough to cause creep corrosion, which is a common mode of electronic hardware failure in environments high in sulfur-bearing gases.
There is a need for a device that will directly detect the presence of atmospheric conditions leading to creep corrosion of PCBs well before the PCBs in the computers start suffering from creep corrosion.